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<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.reference.SerialPortService"></a><a class="link" href="SerialPortService.html" title="Serial port service requirements">Serial port service
      requirements</a>
</h3></div></div></div>
<p>
        A serial port service must meet the requirements for an <a class="link" href="IoObjectService.html" title="I/O object service requirements">I/O
        object service</a> with support for movability, as well as the additional
        requirements listed below.
      </p>
<p>
        In the table below, <code class="computeroutput"><span class="identifier">X</span></code> denotes
        a serial port service class, <code class="computeroutput"><span class="identifier">a</span></code>
        and <code class="computeroutput"><span class="identifier">ao</span></code> denote values of type
        <code class="computeroutput"><span class="identifier">X</span></code>, <code class="computeroutput"><span class="identifier">d</span></code>
        denotes a serial port device name of type <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code>,
        <code class="computeroutput"><span class="identifier">b</span></code> and <code class="computeroutput"><span class="identifier">c</span></code>
        denote values of type <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">implementation_type</span></code>, <code class="computeroutput"><span class="identifier">n</span></code>
        denotes a value of type <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">native_handle_type</span></code>,
        <code class="computeroutput"><span class="identifier">ec</span></code> denotes a value of type
        <code class="computeroutput"><span class="identifier">error_code</span></code>, <code class="computeroutput"><span class="identifier">s</span></code> denotes a value meeting <a class="link" href="SettableSerialPortOption.html" title="Settable serial port option requirements"><code class="computeroutput"><span class="identifier">SettableSerialPortOption</span></code></a> requirements,
        <code class="computeroutput"><span class="identifier">g</span></code> denotes a value meeting
        <a class="link" href="GettableSerialPortOption.html" title="Gettable serial port option requirements"><code class="computeroutput"><span class="identifier">GettableSerialPortOption</span></code></a> requirements,
        <code class="computeroutput"><span class="identifier">mb</span></code> denotes a value satisfying
        <a class="link" href="MutableBufferSequence.html" title="Mutable buffer sequence requirements">mutable buffer
        sequence</a> requirements, <code class="computeroutput"><span class="identifier">rh</span></code>
        denotes a value meeting <a class="link" href="ReadHandler.html" title="Read handler requirements"><code class="computeroutput"><span class="identifier">ReadHandler</span></code></a> requirements, <code class="computeroutput"><span class="identifier">cb</span></code> denotes a value satisfying <a class="link" href="ConstBufferSequence.html" title="Constant buffer sequence requirements">constant
        buffer sequence</a> requirements, and <code class="computeroutput"><span class="identifier">wh</span></code>
        denotes a value meeting <a class="link" href="WriteHandler.html" title="Write handler requirements"><code class="computeroutput"><span class="identifier">WriteHandler</span></code></a> requirements. and
        <code class="computeroutput"><span class="identifier">u</span></code> and <code class="computeroutput"><span class="identifier">v</span></code>
        denote identifiers.
      </p>
<div class="table">
<a name="boost_asio.reference.SerialPortService.t0"></a><p class="title"><b>Table&#160;25.&#160;SerialPortService requirements</b></p>
<div class="table-contents"><table class="table" summary="SerialPortService requirements">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  expression
                </p>
              </th>
<th>
                <p>
                  return type
                </p>
              </th>
<th>
                <p>
                  assertion/note<br> pre/post-condition
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">native_handle_type</span></code>
                </p>
              </td>
<td>
              </td>
<td>
                <p>
                  The implementation-defined native representation of a serial port.
                  Must satisfy the requirements of <code class="computeroutput"><span class="identifier">CopyConstructible</span></code>
                  types (C++ Std, 20.1.3), and the requirements of <code class="computeroutput"><span class="identifier">Assignable</span></code> types (C++ Std, 23.1).
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">construct</span><span class="special">(</span><span class="identifier">b</span><span class="special">);</span></code>
                </p>
              </td>
<td>
              </td>
<td>
                <p>
                  From <a class="link" href="IoObjectService.html" title="I/O object service requirements">IoObjectService</a>
                  requirements.<br> post: <code class="computeroutput"><span class="special">!</span><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">destroy</span><span class="special">(</span><span class="identifier">b</span><span class="special">);</span></code>
                </p>
              </td>
<td>
              </td>
<td>
                <p>
                  From <a class="link" href="IoObjectService.html" title="I/O object service requirements">IoObjectService</a>
                  requirements. Implicitly cancels asynchronous operations, as if
                  by calling <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">close</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span>
                  <span class="identifier">ec</span><span class="special">)</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">move_construct</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">c</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
              </td>
<td>
                <p>
                  From <a class="link" href="IoObjectService.html" title="I/O object service requirements">IoObjectService</a>
                  requirements. The underlying native representation is moved from
                  <code class="computeroutput"><span class="identifier">c</span></code> to <code class="computeroutput"><span class="identifier">b</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">move_assign</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">ao</span><span class="special">,</span> <span class="identifier">c</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
              </td>
<td>
                <p>
                  From <a class="link" href="IoObjectService.html" title="I/O object service requirements">IoObjectService</a>
                  requirements. Implicitly cancels asynchronous operations associated
                  with <code class="computeroutput"><span class="identifier">b</span></code>, as if by
                  calling <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">close</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span>
                  <span class="identifier">ec</span><span class="special">)</span></code>.
                  Then the underlying native representation is moved from <code class="computeroutput"><span class="identifier">c</span></code> to <code class="computeroutput"><span class="identifier">b</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&amp;</span> <span class="identifier">u</span> <span class="special">=</span> <span class="identifier">d</span><span class="special">;</span>
<span class="identifier">a</span><span class="special">.</span><span class="identifier">open</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">u</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">error_code</span></code>
                </p>
              </td>
<td>
                <p>
                  pre: <code class="computeroutput"><span class="special">!</span><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.<br> post: <code class="computeroutput"><span class="special">!!</span><span class="identifier">ec</span> <span class="special">||</span>
                  <span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">assign</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">n</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">error_code</span></code>
                </p>
              </td>
<td>
                <p>
                  pre: <code class="computeroutput"><span class="special">!</span><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.<br> post: <code class="computeroutput"><span class="special">!!</span><span class="identifier">ec</span> <span class="special">||</span>
                  <span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="keyword">bool</span></code>
                </p>
              </td>
<td>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="keyword">const</span> <span class="identifier">X</span><span class="special">&amp;</span> <span class="identifier">u</span> <span class="special">=</span> <span class="identifier">a</span><span class="special">;</span>
<span class="keyword">const</span> <span class="identifier">X</span><span class="special">::</span><span class="identifier">implementation_type</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">=</span> <span class="identifier">b</span><span class="special">;</span>
<span class="identifier">u</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="keyword">bool</span></code>
                </p>
              </td>
<td>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">close</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">error_code</span></code>
                </p>
              </td>
<td>
                <p>
                  If <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">()</span></code>
                  is true, causes any outstanding asynchronous operations to complete
                  as soon as possible. Handlers for cancelled operations shall be
                  passed the error code <code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">operation_aborted</span></code>.<br>
                  post: <code class="computeroutput"><span class="special">!</span><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">native_handle</span><span class="special">(</span><span class="identifier">b</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">native_handle_type</span></code>
                </p>
              </td>
<td>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">cancel</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">error_code</span></code>
                </p>
              </td>
<td>
                <p>
                  pre: <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.<br>
                  Causes any outstanding asynchronous operations to complete as soon
                  as possible. Handlers for cancelled operations shall be passed
                  the error code <code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">operation_aborted</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">set_option</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">s</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">error_code</span></code>
                </p>
              </td>
<td>
                <p>
                  pre: <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">get_option</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">g</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">error_code</span></code>
                </p>
              </td>
<td>
                <p>
                  pre: <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="keyword">const</span> <span class="identifier">X</span><span class="special">&amp;</span> <span class="identifier">u</span> <span class="special">=</span> <span class="identifier">a</span><span class="special">;</span>
<span class="keyword">const</span> <span class="identifier">X</span><span class="special">::</span><span class="identifier">implementation_type</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">=</span> <span class="identifier">b</span><span class="special">;</span>
<span class="identifier">u</span><span class="special">.</span><span class="identifier">get_option</span><span class="special">(</span><span class="identifier">v</span><span class="special">,</span> <span class="identifier">g</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">error_code</span></code>
                </p>
              </td>
<td>
                <p>
                  pre: <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">send_break</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">error_code</span></code>
                </p>
              </td>
<td>
                <p>
                  pre: <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">read_some</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span>
                  <span class="identifier">mb</span><span class="special">,</span>
                  <span class="identifier">ec</span><span class="special">);</span></code>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">size_t</span></code>
                </p>
              </td>
<td>
                <p>
                  pre: <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.<br>
                  <br> Reads one or more bytes of data from a serial port <code class="computeroutput"><span class="identifier">b</span></code>.<br> <br> The mutable buffer
                  sequence <code class="computeroutput"><span class="identifier">mb</span></code> specifies
                  memory where the data should be placed. The operation shall always
                  fill a buffer in the sequence completely before proceeding to the
                  next.<br> <br> If successful, returns the number of bytes read.
                  Otherwise returns <code class="computeroutput"><span class="number">0</span></code>.
                  If the total size of all buffers in the sequence <code class="computeroutput"><span class="identifier">mb</span></code> is <code class="computeroutput"><span class="number">0</span></code>,
                  the function shall return <code class="computeroutput"><span class="number">0</span></code>
                  immediately.<br> <br> If the operation completes due to graceful
                  connection closure by the peer, the operation shall fail with
                  <code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">eof</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">async_read_some</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span>
                  <span class="identifier">mb</span><span class="special">,</span>
                  <span class="identifier">rh</span><span class="special">);</span></code>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="keyword">void</span></code>
                </p>
              </td>
<td>
                <p>
                  pre: <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.<br>
                  <br> Initiates an asynchronous operation to read one or more
                  bytes of data from a serial port <code class="computeroutput"><span class="identifier">b</span></code>.
                  The operation is performed via the <code class="computeroutput"><span class="identifier">io_service</span></code>
                  object <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">get_io_service</span><span class="special">()</span></code>
                  and behaves according to <a class="link" href="asynchronous_operations.html" title="Requirements on asynchronous operations">asynchronous
                  operation</a> requirements.<br> <br> The mutable buffer
                  sequence <code class="computeroutput"><span class="identifier">mb</span></code> specifies
                  memory where the data should be placed. The operation shall always
                  fill a buffer in the sequence completely before proceeding to the
                  next.<br> <br> The implementation shall maintain one or more
                  copies of <code class="computeroutput"><span class="identifier">mb</span></code> until
                  such time as the read operation no longer requires access to the
                  memory specified by the buffers in the sequence. The program must
                  ensure the memory is valid until:<br> <br> &#8212; the last copy of
                  <code class="computeroutput"><span class="identifier">mb</span></code> is destroyed,
                  or<br> <br> &#8212; the handler for the asynchronous operation is invoked,<br>
                  <br> whichever comes first. If the total size of all buffers
                  in the sequence <code class="computeroutput"><span class="identifier">mb</span></code>
                  is <code class="computeroutput"><span class="number">0</span></code>, the asynchronous
                  read operation shall complete immediately and pass <code class="computeroutput"><span class="number">0</span></code> as the argument to the handler
                  that specifies the number of bytes read.<br> <br> If the operation
                  completes due to graceful connection closure by the peer, the operation
                  shall fail with <code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">eof</span></code>.<br>
                  <br> If the operation completes successfully, the <code class="computeroutput"><span class="identifier">ReadHandler</span></code> object <code class="computeroutput"><span class="identifier">rh</span></code> is invoked with the number
                  of bytes transferred. Otherwise it is invoked with <code class="computeroutput"><span class="number">0</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">write_some</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span>
                  <span class="identifier">cb</span><span class="special">,</span>
                  <span class="identifier">ec</span><span class="special">);</span></code>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">size_t</span></code>
                </p>
              </td>
<td>
                <p>
                  pre: <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.<br>
                  <br> Writes one or more bytes of data to a serial port <code class="computeroutput"><span class="identifier">b</span></code>.<br> <br> The constant
                  buffer sequence <code class="computeroutput"><span class="identifier">cb</span></code>
                  specifies memory where the data to be written is located. The operation
                  shall always write a buffer in the sequence completely before proceeding
                  to the next.<br> <br> If successful, returns the number of
                  bytes written. Otherwise returns <code class="computeroutput"><span class="number">0</span></code>.
                  If the total size of all buffers in the sequence <code class="computeroutput"><span class="identifier">cb</span></code> is <code class="computeroutput"><span class="number">0</span></code>,
                  the function shall return <code class="computeroutput"><span class="number">0</span></code>
                  immediately.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">async_write_some</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span>
                  <span class="identifier">cb</span><span class="special">,</span>
                  <span class="identifier">wh</span><span class="special">);</span></code>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="keyword">void</span></code>
                </p>
              </td>
<td>
                <p>
                  pre: <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">is_open</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>.<br>
                  <br> Initiates an asynchronous operation to write one or more
                  bytes of data to a serial port <code class="computeroutput"><span class="identifier">b</span></code>.
                  The operation is performed via the <code class="computeroutput"><span class="identifier">io_service</span></code>
                  object <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">get_io_service</span><span class="special">()</span></code>
                  and behaves according to <a class="link" href="asynchronous_operations.html" title="Requirements on asynchronous operations">asynchronous
                  operation</a> requirements.<br> <br> The constant buffer
                  sequence <code class="computeroutput"><span class="identifier">cb</span></code> specifies
                  memory where the data to be written is located. The operation shall
                  always write a buffer in the sequence completely before proceeding
                  to the next.<br> <br> The implementation shall maintain one
                  or more copies of <code class="computeroutput"><span class="identifier">cb</span></code>
                  until such time as the write operation no longer requires access
                  to the memory specified by the buffers in the sequence. The program
                  must ensure the memory is valid until:<br> <br> &#8212; the last copy
                  of <code class="computeroutput"><span class="identifier">cb</span></code> is destroyed,
                  or<br> <br> &#8212; the handler for the asynchronous operation is invoked,<br>
                  <br> whichever comes first. If the total size of all buffers
                  in the sequence <code class="computeroutput"><span class="identifier">cb</span></code>
                  is <code class="computeroutput"><span class="number">0</span></code>, the asynchronous
                  operation shall complete immediately and pass <code class="computeroutput"><span class="number">0</span></code>
                  as the argument to the handler that specifies the number of bytes
                  read.<br> <br> If the operation completes successfully, the
                  <code class="computeroutput"><span class="identifier">WriteHandler</span></code> object
                  <code class="computeroutput"><span class="identifier">wh</span></code> is invoked with
                  the number of bytes transferred. Otherwise it is invoked with
                  <code class="computeroutput"><span class="number">0</span></code>.
                </p>
              </td>
</tr>
</tbody>
</table></div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2012 Christopher M. Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div></td>
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